Determination of hot-pressing technology parameters for overlaying Red Oak veneers on Acacia hybrid finger joint boards
Keywords:
Acacia hybrid finger joint boards, veneer overlaying technology,, wood-based panels,, surface bonding strength, Oak veneersAbstract
Veneer overlaying technology is the final important step in the production of veneer overlayed wood-based panels. The bonding strength b etween veneers and wood-based panels’ surfaces is influenced by several factors such as pressing parameters (Pressure, Temperature, and Time), types of resin, veneers, and substrates. This study has determined the technology parameters for overlaying red o ak veneers (0.4 mm thickness) on finger joint boards’ surfaces made from Acacia hybrid with a thickness of 12 mm bonded by Melamine urea formaldehyde (MUF) is P = 0.7 MPa; T = 115 o C; τ = 3 minutes with the modulus of rupture (MOR) of 68.2 MPa, and the modulus of elasticity (MOE) of 8.8 GPa which are higher than that of finger joint boards without overlaying veneer 5.6% and 4.5%, respectively. The bonding strength between veneers and surfaces of finger joint boards increased with the increase in processing time, subsequently deceased with the continuous increase in pressing time At the pressure of 0.7 MPa, the bonding strength increased from 1.27 MPa to 1.41 MPa with the increase in pressing time from 2 minutes to 3 minutes, respectively, and then this value decreased to 1.36 MPa with pressing time continuously increasing to 4 minutes. With the resin spread of 100 g/m 2 , The free formaldehyde content released from the surfaces of the finger joint board overlayed veneers on both surfaces is 2.71 mg/L which meets the E2 level according to the Chinese standard GB 18580 - 2001.
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